1. Field of the Invention
The present invention relates to an antenna structure, and more particularly to a multi-band frequency antenna structure used in mobile communication equipment.
2. The Related Art
Antennas are used in various communication systems, such as cellular phones, wireless data and local area network, global system for mobile communications (GSM), and personal communication service (PCS), etc. A clear and strong signal is critical for the wireless communication systems. Therefore, antennas with good performance are required. In order to improve the performance of the antennas, capacitance elements and inductance elements are broadly used in the antennas to adjust a resonance frequency and an impedance matching of the antennas.
Please refer to FIG. 1 showing a conventional antenna structure. The conventional antenna structure includes an antenna body 100 constructed of a first radiating unit 120 and a second radiating unit 130. A feed point 110 is disposed on the antenna body 100 and spaces the first radiating unit 120 and the second radiating unit 130. The first radiating unit 120 extends toward an end of the second radiating unit 130 to form a projection 121. A first capacitor 200 and an inductor 300 are connected in parallel and then connect to the feed point 110 and the ground respectively. The LC parallel connection circuit enables the antenna body 100 and a high-frequency circuit to match with each other. A second capacitor 400 connects with the projection 121 of the first radiating unit 120 and the second radiating unit 130 in series in order to adjust the electrical length of the second radiating unit 130.
If the conventional antenna structure described above is assembled in a hand-held apparatus, the first capacitor 200, the inductor 300 and the second capacitor 400 can be fixed on a PCB of the hand-held apparatus because the antenna and the PCB are adjacent to each other. However, if the antenna structure is assembled in a notebook computer, because the antenna structure is mounted on a top of a monitor of the notebook computer, and a PCB of the notebook computer is disposed on a host of the notebook computer, the distance between the antenna and the PCB is far, then the first capacitor 200, the inductor 300 and the second capacitor 400 can't be disposed on the PCB of the notebook computer and must be integrated with the antenna structure. Therefore, the design and the manufacture of the antenna structure are complex, and the cost is very expensive.